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Biological Explanations Of Deviant Behavior


Deviant behavior is any behavior that is contrary to the dominant norms of society. There are many different theories on what causes a person to perform deviant behavior, including biological explanations, psychological explanations, and sociological explanations. Following are some of the major biological explanations for deviant behavior.

Biological theories of deviance see crime and deviant behavior as a form of illness caused by pathological factors that are specific to certain types of individuals. They assume that some people are "born criminals" who are biologically different than non-criminals. The underlying logic is that these individuals have a mental and physical inferiority, which causes an inability to learn and follow the rules. This in turn leads to criminal behavior.

It should be noted that since their inception, all of the following theories have been discredited.

Lombroso’s Theory

Cesare Lombroso was an Italian criminologist of the mid to late 1800s. He rejected the Classical School, which believed that crime was a characteristic of human nature and instead believed that criminality was inherited. From this belief, he developed a theory of deviance in which a person’s bodily constitution indicates whether or not an individual is a "born criminal." These "born criminals" are a throwback to an earlier stage of human evolution with the physical makeup, mental capabilities, and instincts of primitive man.

In developing his theory, Lombroso observed the physical characteristics of Italian prisoners and compared them to those of Italian soldiers. He concluded that the criminals were physically different. The physical characteristics that he used to identify prisoners included an asymmetry of the face or head, large monkey-like ears, large lips, a twisted nose, excessive cheekbones, long arms, and excessive wrinkles on the skin. Lombroso declared that males with five or more of these characteristics could be marked as born criminals. Females, on the other hand, only needed as few as three of these characteristics to be born criminals.

Lombroso also believed that tattoos were markings of born criminals because they stood as evidence of both immortality and insensitivity to physical pain.

Sheldon’s Theory of Body Types

William Sheldon was an American psychologist from the early to mid 1900s who spent his life observing the varieties of human bodies. As a result, he came up with three types of human bodies: ectomorphs, endomorphs, and mesomorphs.

Ectomorphs are thin and fragile. Their body is described as flat-chested, fragile, lean, lightly muscled, small shouldered, and thin. Celebrities that could be described as ectomorphs include Kate Moss, Edward Norton, and Lisa Kudrow.

Endomorphs are considered soft and fat. They are described as having a soft body, underdeveloped muscles, a round physique, and they often have difficulty losing weight. John Goodman, Roseanne Barr, and Jack Black are all celebrities that would be considered endomorphs.

Mesomorphs are muscular and athletic. Their body is described as hourglass shaped (female) or rectangular shaped (male), muscular, has excellent posture, gains muscle easily, and has thick skin. Famous mesomorphs include Bruce Willis and Sylvester Stallone. Mesomorphs, according to Sheldon, are the most prone to commit crime or deviant behaviors.

Y Chromosome Theory

The extra Y chromosome theory is the belief that criminals have an extra Y chromosome, giving them an XYY chromosome makeup rather than an XY makeup, that creates a strong compulsion within them to commit crimes. This person is sometimes called the "super male." Some studies have found that the proportion of XYY males in the prison population is higher than the general male population (1 to 3 percent versus less than 1 percent), however other studies don’t provide evidence that supports this theory.


BarCharts, Inc. (2000). Sociology: The Basic Principles of Sociology for Introductory Courses. Boca Raton, FL: Bar Charts, Inc.

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